Immune thrombocytopenia (ITP)

Immune thrombocytopenia (ITP): (same as immune thrombocytopenic purpura)

  • Diagnosis of exclusion characterized by isolated thrombocytopenia in an otherwise healthy young adult with lack of cause for thrombocytopenia or in child with viral illness.
    • Clinical diagnosis: Do not need bone marrow biopsy for evaluation. Do not need antiplatelet antibodies, platelet survival times, or the degree of increase in platelet count after platelet transfusion.
      • Need bone marrow biopsy:
        • If patient is > 60 years old to rule out Myelodysplasia (as the cause for thrombocytopenia).
        • If patient does not respond to prednisone.
  • Peripheral smear: Giant platelets.
  • Causes: Drug related or Autoimmune, HIV, SLE, Hepatitis, H. pylori, or pregnancy
    • Autoantibody-mediated destruction of platelets
      • Autoantibodies also affect megakarytocytes and impair platelet production
    • Primary ITP: Acquired thrombocytopenia due to autoimmune platelet destruction, not triggered by an associated condition. No identifiable cause.
      • Immune destruction in the spleen leading to reduced platelet survival.
    • Secondary ITP: ITP associated with another condition
      • Ex: HIV, Hepatitis C virus, SLE, CLL.
      • By convention, the associated condition is noted in parenthesis, as in “secondary ITP (lupus-associated).”
    • Drug-induced ITP: Drug reaction due to drug-dependent platelet antibodies that cause platelet destruction. This syndrome should be distinguished from drug-induced bone marrow suppression, a non-immune phenomenon.
      • Medication Ex: Gold, Quinine, beta-lactam antibiotics.
  • Sx: Petechiae, purpura, mucosal bleeding, menorrhagia
  • Normal sized spleen.
  • Start Tx when Platelets of 30,000-40,000 (<30,000) or active bleeding.
    • No Tx needed if: Platelets > 30,000 and no active bleeding. [Observation.]
    • Avoid transfusing platelets unless the patient is actively bleeding.
    •  Treatment:
      • 1st: Steroids (Prednisone) 1mg/kg/day x 4-6 weeks: Use for initial Tx of newly diagnosed patients. Time to remission is 1-3 weeks. 1st line treatment but 90% will relapse.
        • If risk for acute bleeding: IVIg 1g/kg x 1 or 0.4g/kg/day x 2. Rapid remission but short-lived. Also, if acute bleeding, platelets can be transfused.
      • 2nd: Rituximab 375mg/m2 q 1 week x 4 doses
        • 30% response rate in chronic refractory ITP
        • Can cause allergic reactions.
      • Thrombopoietin-receptor agonists (TPO-RAs) have been approved for use in ITP after showing safety and efficacy.
      • Other:
        • Danazol 600mg/day
        • Anti-RhD 50 microgram/kg x 1
          • Induces hemolytic anemia
          • Works only with Rh +
        • Last line: Splenectomy – may require looking for an accessory spleen (small nodule of splenic tissue found apart from main spleen).
          • Refractory to steroids -> Splenectomy is the most effective way to induce remission.

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